py: Add full traceback to exception printing.

py/obj.c

@@ -58,6 +58,22 @@ void mp_obj_print(mp_obj_t o_in, mp_print_kind_t kind) {
     mp_obj_print_helper(printf_wrapper, NULL, o_in, kind);
 }
 
+// helper function to print an exception with traceback
+void mp_obj_print_exception(mp_obj_t exc) {
+    if (MP_OBJ_IS_TYPE(exc, &exception_type)) {
+        machine_uint_t n, *values;
+        mp_obj_exception_get_traceback(exc, &n, &values);
+        if (n > 0) {
+            printf("Traceback (most recent call last):\n");
+            for (int i = n - 3; i >= 0; i -= 3) {
+                printf("  File \"%s\", line %d, in %s\n", qstr_str(values[i]), (int)values[i + 1], qstr_str(values[i + 2]));
+            }
+        }
+    }
+    mp_obj_print(exc, PRINT_REPR);
+    printf("\n");
+}
+
 bool mp_obj_is_callable(mp_obj_t o_in) {
     if (MP_OBJ_IS_SMALL_INT(o_in)) {
         return false;

py/obj.h

@@ -236,6 +236,7 @@ const char *mp_obj_get_type_str(mp_obj_t o_in);
 
 void mp_obj_print_helper(void (*print)(void *env, const char *fmt, ...), void *env, mp_obj_t o_in, mp_print_kind_t kind);
 void mp_obj_print(mp_obj_t o, mp_print_kind_t kind);
+void mp_obj_print_exception(mp_obj_t exc);
 
 bool mp_obj_is_callable(mp_obj_t o_in);
 machine_int_t mp_obj_hash(mp_obj_t o_in);
@@ -273,8 +274,8 @@ machine_int_t mp_obj_int_get_checked(mp_obj_t self_in);
 // exception
 extern const mp_obj_type_t exception_type;
 qstr mp_obj_exception_get_type(mp_obj_t self_in);
-void mp_obj_exception_set_source_info(mp_obj_t self_in, qstr file, machine_uint_t line, qstr block);
-void mp_obj_exception_get_source_info(mp_obj_t self_in, qstr *file, machine_uint_t *line, qstr *block);
+void mp_obj_exception_add_traceback(mp_obj_t self_in, qstr file, machine_uint_t line, qstr block);
+void mp_obj_exception_get_traceback(mp_obj_t self_in, machine_uint_t *n, machine_uint_t **values);
 
 // str
 extern const mp_obj_type_t str_type;

py/objexcept.c

@@ -17,9 +17,7 @@
 // have args tuple (or otherwise have it as NULL).
 typedef struct mp_obj_exception_t {
     mp_obj_base_t base;
-    qstr source_file;
-    machine_uint_t source_line;
-    qstr source_block;
+    mp_obj_t traceback; // a list object, holding (file,line,block) as numbers (not Python objects); a hack for now
     qstr id;
     qstr msg;
     mp_obj_tuple_t args;
@@ -90,8 +88,7 @@ mp_obj_t mp_obj_new_exception_msg_varg(qstr id, const char *fmt, ...) {
     // make exception object
     mp_obj_exception_t *o = m_new_obj_var(mp_obj_exception_t, mp_obj_t*, 0);
     o->base.type = &exception_type;
-    o->source_file = 0;
-    o->source_line = 0;
+    o->traceback = MP_OBJ_NULL;
     o->id = id;
     o->args.len = 0;
     if (fmt == NULL) {
@@ -115,26 +112,27 @@ qstr mp_obj_exception_get_type(mp_obj_t self_in) {
     return self->id;
 }
 
-void mp_obj_exception_set_source_info(mp_obj_t self_in, qstr file, machine_uint_t line, qstr block) {
+void mp_obj_exception_add_traceback(mp_obj_t self_in, qstr file, machine_uint_t line, qstr block) {
     assert(MP_OBJ_IS_TYPE(self_in, &exception_type));
     mp_obj_exception_t *self = self_in;
-    // TODO make a list of file/line pairs for the traceback
-    // for now, just keep the first one
-    if (file != 0 && self->source_file == 0) {
-        self->source_file = file;
-    }
-    if (line != 0 && self->source_line == 0) {
-        self->source_line = line;
-    }
-    if (block != 0 && self->source_block == 0) {
-        self->source_block = block;
+    // for traceback, we are just using the list object for convenience, it's not really a list of Python objects
+    if (self->traceback == MP_OBJ_NULL) {
+        self->traceback = mp_obj_new_list(0, NULL);
     }
+    mp_obj_list_append(self->traceback, (mp_obj_t)(machine_uint_t)file);
+    mp_obj_list_append(self->traceback, (mp_obj_t)(machine_uint_t)line);
+    mp_obj_list_append(self->traceback, (mp_obj_t)(machine_uint_t)block);
 }
 
-void mp_obj_exception_get_source_info(mp_obj_t self_in, qstr *file, machine_uint_t *line, qstr *block) {
+void mp_obj_exception_get_traceback(mp_obj_t self_in, machine_uint_t *n, machine_uint_t **values) {
     assert(MP_OBJ_IS_TYPE(self_in, &exception_type));
     mp_obj_exception_t *self = self_in;
-    *file = self->source_file;
-    *line = self->source_line;
-    *block = self->source_block;
+    if (self->traceback == MP_OBJ_NULL) {
+        *n = 0;
+        *values = NULL;
+    } else {
+        uint n2;
+        mp_obj_list_get(self->traceback, &n2, (mp_obj_t**)values);
+        *n = n2;
+    }
 }

py/vm.c

@@ -544,7 +544,7 @@ bool mp_execute_byte_code_2(const byte *code_info, const byte **ip_in_out, mp_ob
                         break;
                     }
                 }
-                mp_obj_exception_set_source_info(nlr.ret_val, source_file, source_line, block_name);
+                mp_obj_exception_add_traceback(nlr.ret_val, source_file, source_line, block_name);
             }
 
             while (currently_in_except_block) {

stm/main.c

@@ -445,8 +445,7 @@ void do_repl(void) {
                     }
                 } else {
                     // uncaught exception
-                    mp_obj_print((mp_obj_t)nlr.ret_val, PRINT_REPR);
-                    printf("\n");
+                    mp_obj_print_exception((mp_obj_t)nlr.ret_val);
                 }
             }
         }
@@ -490,8 +489,7 @@ bool do_file(const char *filename) {
         return true;
     } else {
         // uncaught exception
-        mp_obj_print((mp_obj_t)nlr.ret_val, PRINT_REPR);
-        printf("\n");
+        mp_obj_print_exception((mp_obj_t)nlr.ret_val);
         return false;
     }
 }

unix/main.c

@@ -73,15 +73,7 @@ static void execute_from_lexer(mp_lexer_t *lex, mp_parse_input_kind_t input_kind
         nlr_pop();
     } else {
         // uncaught exception
-        mp_obj_t exc = (mp_obj_t)nlr.ret_val;
-        if (MP_OBJ_IS_TYPE(exc, &exception_type)) {
-            qstr file, block;
-            machine_uint_t line;
-            mp_obj_exception_get_source_info(exc, &file, &line, &block);
-            printf("File \"%s\", line %d, in %s\n", qstr_str(file), (int)line, qstr_str(block));
-        }
-        mp_obj_print(exc, PRINT_REPR);
-        printf("\n");
+        mp_obj_print_exception((mp_obj_t)nlr.ret_val);
     }
 }